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Light intensity, egg weight and egg size in a vertical aviary of naturally ventilated laying hens
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.orgCitation: 10th International Livestock Environment Symposium (ILES X) .(doi:10.13031/iles.18-149)
Authors: LETÍCIA CIBELE S R FREITAS, ILDA DE FÁTIMA FERREIRA TINÔCO, TATIANY CARVALHO DOS SANTOS, MÁRCIA GABRIELLE LIMA CÂNDIDO, CECÍLIA DE FÁTIMA SOUZA, RICHARD STEPHEN GATES
Keywords: Environment, Lighting, Egg quality.
Abstract. Light intensity is an important variable for the reproductive performance of laying hens. A hen´s reproductive system is stimulated by photoreceptors that affect egg production and quality. Photostimulation occurs through photoreceptors located in the eyes (retina), skull (hypothalamus and pituitary glands) and transcranial (bones) of birds. The light intensity in naturally ventilated, vertical caged aviaries can vary due to the position of the cages, which are barriers to light penetration. The objective of this study was to analyze the spatial distribution of light intensity in a typical naturally ventilated, vertical caged aviary and corresponding egg weight and size during tropical winter and summer seasons. The research was conducted in a commercial aviary with galvanized steel frames and uninsulated steel roof panels. The dimensions were 134 m x 12.5 m (length x width), with a 5 m height, and 1.2 m wide covered open ridge. Inside the facilities, there were four rows of vertical cages, each with six tiers of cages. Each cage was 0.6 m x 0.5 m x 0.4 m (width x depth x height), housing 8 to 10 birds per cage at an average density of 300-375 cm².bird-¹. The aviary can house up to 100,000 laying hens (Hy-Line W-36). Light intensity data were collected at 25 points distributed evenly across the longitudinal direction of the aviary and in three tiers of cages (first, third and sixth); totaling 75 collection points. To analyze the external quality of the eggs, the size (major and minor diameter) and of eggs were obtained from the same positions where the intensity was collected. There was a significant difference between the values of intensity (P <0.001) obtained on the sides of the aviary and on the sixth tier of cages in relation to the center and the first floor cages. The egg weight and minor diameter were different (P <0.001) between the cage tiers and the season of the year. In winter, the eggs on the first tier of cages had higher weights and smaller diameters. The egg weight and size were larger where the light intensity was close to the recommended level (30 lux), that is, in the first tier of cages, suggesting that much of the aviary is over-illuminated.(Download PDF) (Export to EndNotes)